1. FIELD OF THE INVENTION
This invention relates to improvements in methods and apparatuses for Controlling the speed and delay of windshield wipers, and more particularly to improvements in methods and apparatuses for precisely establishing the delay of windshield wiper operation and controlling the speed of the windshield wiper driving motor.
2. DESCRIPTION OF THE RELEVANT BACKGROUND
Modern windshield wiper controls typically provide two windshield 10 wiper speeds. The speeds are usually realized by a motor having two field windings arranged such that one winding produces a faster motor speed than the other. The wiper speed is therefore controlled by selectively energizing one or the other of the windings. A typical prior art windshield wiper system 10 is shown in FIG. 1. In the prior art system 10, a motor 11 has two field coil windings, one or the other of which can be selected by closing one or the other of switches 13 or 14 to complete the circuit with the battery 15.
Some windshield wiper controls provide an intermittent capability in which a delay is established between successive wipes by the wipers. The common way by which such delay is accomplished is by a variable resistor 20 to provide a variable RC time constant to drive a relay 22 according to the particular delay selected.
Typical prior art windshield wiper control systems, however, have several undesirable aspects. For example, since mechanical switches and relays are ordinarily used, electrical noise often accompanies windshield wiper operation. Such electrical noise may interfere with other electrical systems in the vehicle on which the windshield wiper control system is employed. Also, the delay provided by most windshield wiper drivers is difficult to adjust for various weather conditions for comfortable driving. Usually, the adjustment is a "cut and try" approach in which the operator selects an arbitrary windshield wiper delay. After the operator observes the effectiveness of the windshield wiper action makes an adjustment in the delay to produce a windshield wiping timing that maintains a clear windshield without unnecessary wiping. Usually PG,3 one or more iterations are required to arrive at the ultimate adjustment for the particular windshield wiping delay.